Beijing played the role of broker in a historic deal that Iran yesterday struck with six world powers aimed at curbing Tehran's nuclear programme in exchange for initial sanctions relief.

The agreement is the most significant development between the United States and Iran in more than three decades of estrangement between the nations.

China is one of the five UN Security Council committee members who along with Germany negotiated the deal for Tehran to limit uranium enrichment to low levels.

Analysts say China pulled off a delicate balancing act in the negotiations between Iran, seen by Beijing as a long-term partner, and the US.

Hua Liming, the former Chinese ambassador to Iran, told state media that China acted as a helping broker. "When the two parties came across irresolvable problems, they would come to China, which would 'lubricate' the negotiation and put things back on track," he said.

This agreement will ... safeguard peace and stability in the Middle East

WANG YI, FOREIGN MINISTER

Beijing welcomed the breakthrough deal with Iran, saying it would "help safeguard peace and stability in the Middle East".

"This agreement will help to uphold the international nuclear non-proliferation system [and] safeguard peace and stability in the Middle East," Foreign Minister Wang Yi said in Geneva.

The US said the deal would halt advances in Iran's nuclear programme, including construction of the Arak heavy-water reactor that could yield plutonium, a vital ingredient in atomic weapons.

It would neutralise Iran's stockpile of uranium refined to a concentration of 20 per cent, which is a close step away from the level needed for weapons, and calls for enhanced, more frequent UN nuclear inspections.

While Iran could obtain access to US$1.5 billion in revenue from trade in gold and precious metals as a result of the easing of sanctions, its crude oil sales would still be limited to about one million barrels a day.

US President Barack Obama said the deal cut off Tehran's potential path to a nuclear weapon. But Israel, Iran's arch-enemy, denounced the agreement as an "historic mistake".

"Today the world has become a much more dangerous place because the most dangerous regime in the world took a significant step towards obtaining the world's most dangerous weapon," said Benjamin Netanyahu, Israel's prime minister.

Jin Canrong , of Renmin University's school of international studies, said China played a supporting role in talks.

"The US and Europe all had a lot of sanctions against Iran, which they are accusing of making nuclear weapons. China has been out of the dispute," he said.

Xiao Xian , an expert in international politics at Yunnan University, said regional stability was in China's long-term interest because it would enjoy more secure natural resources from Iran.